Muscular Analysis of Movement Chapter 14, pp.260-264 Chapter 17
System Level Function • Force & torque production for joint mobility and stability through rotation and translation of bones (segments) • Muscle Actions • Muscle Coordination (Synergy)
Related Terminology • muscle action – the development of tension (force) by a muscle • functional muscle group – a group of muscles that are capable of causing a specific joint action (e.g., wrist radial deviators) • motive force (or torque) – force causing the observed movement • resistive force (or torque) – force opposing the observed movement
Types of Muscle Actions • Concentric • Eccentric • Isometric
Concentric • Shortens to cause movement • Rotational movement • Mechanically: Net Muscle (Motive) Torque > Net Resistive Torque
Eccentric • Lengthens to resist, control, or slow down movement • Rotational movement • Mechanically: Net Muscle (Resistive) Torque < Net Motive Torque
Isometric • Stays the same so that bone will stay fixed • No movement • Mechanically: Net Muscle Torque = Other Torque Total Net Torque = 0
System Level: Muscle Actions • Resulting motion dependent on all torques acting about the joint (net torque) Conditions for concentric? Eccentric? Isometric?
Muscle Coordination: Roles that Muscles Play • Agonists • Antagonists • Stabilizers • Neutralizers
Arbitrary distinction Agonist (Mover) • The role played by a muscle acting to cause a movement • Prime movers • Assistant movers • Force development during concentric action • Relaxation during eccentric action
Antagonist • The role played by a muscle acting • to control movement of a body segment against some other non-muscle force • to slow or stop a movement • Force development during eccentric action • Check ballistic movements • Relaxation during concentric action
Stabilizer • The role played by a muscle to stabilize (fixate) a body part against some other force • rotary (joint) stabilizer • linear (bone) stabilizer • Isometric muscle action
Neutralizer • The role played by a muscle to eliminate an unwanted action produced by an agonist • Scapular or pelvic stabilization • Multijoint muscles • Elevation of the humerus • Muscle action varies
To perform a muscular analysis: • Break the skill into phases. • Determine the joint action? • Determine the motive force – muscle or some other force? • Determine the resistive force – muscle or some other force?
To perform a muscular analysis (ID muscle actions and responsible groups): • Identify whether there are joints/bones that must be stabilized • Identify • the FMG(s) that is(are) developing force • the type of muscle action of the FMG(s) • the roles played by the FMG(s) • Identify neutralization.
Example 1: Biceps Curl Flexion Muscle Weight/Gravity Elbow Flexors Concentric
Example 1: Biceps Curl Flexion Extension Weight/Gravity Muscle Muscle Weight/Gravity Elbow Flexors Elbow Flexors Concentric Eccentric
Example 1: Biceps Curl Agonists: Flexors Extensors Flexion Extension Weight/Gravity Muscle Muscle Weight/Gravity Elbow Flexors Elbow Flexors Concentric Eccentric
Example 1: Biceps Curl Antagonists: Extensors Flexors Flexion Extension Weight/Gravity Muscle Muscle Weight/Gravity Elbow Flexors Elbow Flexors Concentric Eccentric
Stabilization? • Rotary stabilization • Wrist flexors • Linear stabilization
Neutralization? • To prevent scapular or pelvic movement when moving humerus or femur • Shoulder girdle retractors • Shoulder girdle elevators • To prevent unwanted motion caused by multijoint muscles • Shoulder extensors • Forearm pronators
Neutralization • To prevent scapular movement during elevation of the humerus • Other? • Biceps brachii – shoulder flexion, RU supination • Brachialis – none • Brachioradialis – RU motion • Pronator teres – RU pronation
Summary • Movement at a single joint is possible because of the complex coordination that occurs between numerous muscles. • Therefore, all those muscles must have adequate strength to accomplish its task in a given movement. • Injury to or lack of strength in any of those muscles can result in the inability to perform the movement.
Summary • A muscular analysis allows us to identify the muscles that contribute to a movement and how they contribute to the movement. • We can then prepare conditioning & rehabilitation programs that target utilized muscles appropriately.